The Fischer-Tropsch synthesis (FTS) is a process by which synthetic gas or syngas, comprising carbon monoxide and hydrogen, is converted into liquid hydrocarbon fuels like synthetic diesel and jet fuel. Prior to the FTS process, the coal, gas or biomass feed stocks are gasified using intense heat and pressure in order to produce the syngas for the FTS process. The synthetic fuels resulting from the FTS process advantageously increase energy diversity. They also burn cleanly and thus hold the promise of improved environmental performance.
Currently there is a greatly renewed interest in large scale development of FTS plants to convert coal, biomass and other feed stocks into liquid fuels. While state of the art FTS processes produce a very clean fuel, they also, unfortunately, produce significant emissions of carbon dioxide. This is because coal-derived syngas typically only has H2/CO ratios in the range of approximately 0.6 to 1.1, dependent on the method of gasification and the ratio of steam to oxygen used to oxidize the coal or other feedstocks in the gasification unit.
State of the art FTS technology relies on the water-gas shift (WGS) reaction to raise the hydrogen to carbon monoxide molar ratio (H2/CO) of the syngas to values of 2.0 or higher that are needed for the FTS process. This, unfortunately, produces one CO2 molecule for each H2 molecule added to the syngas. Unless the CO2 produced by the FTS process is captured and stored, for example, underground, state of the art FTS processes add large amounts of CO2 to the atmosphere, thereby increasing the greenhouse effect. Currently, the only way to prevent this undesirable result is to capture and store the carbon dioxide. Systems for the capture and storage of carbon dioxide, including proposed underground storage systems, are, unfortunately, quite expensive, largely untested, and add significant cost to the synthetic fuel production process.
The present invention relates to a modified and improved FTS process wherein the carbon byproduct produced by the FTS process is in the form of potentially valuable carbon multi-walled nanotubes (MWNT) instead of environmentally troubling carbon dioxide. Thus, the present invention represents a significant advance in the art allowing for the more efficient, effective, economical and environmentally friendly manufacture of synthetic fuels as an alternative fuel supply.